Keyslot reamer



W. S. CRAKE KEYSLOT REAMER Dec. 20, 1955 mam V,

INVENTOR Filed June 7, 1954 rrrrrl l WILFRED s. CRAKE FIG. Bwwflr/ HIS ATTORNEY United States Patent Ofiice 2,727,730 Patented Dec. 20, 1955 KEYSLOT REAMER Wilfred S. Crake, Houston, Tex., ass'ignor to Shell Developinent Company, New York, N. Y., a cer eration of Delaware Application June 7, 1954, Serial No. 434,716

4 Claims. (Cl. 255-73) This invention relates to the drilling of deep oil and gas wells, and pertains more particularly to a keyslot reamer or enlarger for use with drilling strings.

In drilling wells by the rotary method, it is not always possible to maintain a straight or vertical borehole. However, crooked boreholes or boreholes deviating from the vertical may be brought back to the desired direction by changing the Weight on the bit or by using means such as whipstocks, knuckle joints, etc. In such cases, there is usually formed in the borehole a so-called dog-leg, which may be defined as the crooked or deflected portion of the borehole joining an upper substantially straight or vertical portion with a lower substantially straight or vertical portion of said borehole. As the drilling proceeds at a level below the dog-leg, the drill string, rotating and rubbing against a shoulder of the borehole wall, wears or cuts therein a groove or slot known as a keyslot. Since the keyslot is formed by the drill string at a time when the drill bit and the larger diameter collars proximate thereto are already below the dog-leg, the di ameter of the keyslot generally corresponds to that of the drill string, and is therefore smaller than that of said drill bit and collars. Thus, when it is desired, for any reason whatsoever, to raise the drill bit to the surface, it often happens that the lower portion of the drill string becomes stuck or wedged in a keyslot, either causing a rupture of the string, or necessitating complex salvaging operations.

It is therefore an object of this invention to provide a tool connectable into a drill string and capable of freeing said drill string from a keyslot by enlarging the diameter of said keyslot.

It is also an object to provide a keyslot reamer capable of achieving this purpose by utilizing both reciprocating and rotary cutting action.

It is also an object of this invention to provide a keyslot reamer having circular broaching or cutting shoulders or edges parallel to each other and perpendicular to the longitudinal axis of the tool, and also spiral slicing edges or grooves formed on the tool slantingly across said broaching edges, the angle of slant of said spiral grooves being preferably about 60 degrees in projection with regard to the longitudinal axis or center line of the keyslot reamer.

It is an object of this invention to provide a keyslot reamer of relatively short axial length and simple design, which can be easily handled under all circumstances, and is inexpensive to manufacture.

These and other objects of this invention will be understood from the following description taken with reference to the attached drawings, wherein:

Fig. 1 is a view, partly in cross-section, of the present keyslot reamer;

Fig. 1a is a fractional elevation view showing the broaching shoulders but omitting for clarity the spiral grooves machined across these shoulders;

Fig. 2 is a transverse cross-section view taken along line 2-2 of Fig. l,

Referring to the drawings, the present keyslot reamer has the shape of a tubular mandrel 11 adapted to be connected into a drill string by means such as upper inside screw threads 13 and lower outside screw threads 15. An axial passage 17 is provided through the reamer for the circulation of drilling fluid.

The present reamer has no eentinuqus or wedging taper, but a series, SUCh 3S flGiI-l 6 t6) 24 01 more, Of annular ShOulder's' generally S liC iWIl 3t 19, i3 fofiiie'd thereon. These shoulders may have a width such as from f to of an iliii and are spaced from each other by comparatively substantial distances of an order such as 2 inches. If, ft ir example, 12 shoulders are used, as shown in Fig. 1, the lower or thick end of the tool may have a diameter about 1% inches larger than the upper or thin end ofthe tool. The tool, which may have a maximum diameter of from 6 to 9 inches and an overall length from 3 to 6 feet or more, is machined of a material such as cast steel, the outer rims of the shoulders 19 being formed as sharp cutting or broaching edges.

Milled or otherwise machined in the cylindrical face of the reamer and across the stepwise series of shoulders thereon, are spiral grooves 21, which are formed with their center line disposed at an angle such as 45 degrees, and preferably 60 degrees, but not more than degrees, with regard to the axial line of the tool, and therefore at an angle such as 45 and preferably 30, but not less than 15, degrees with the edges of the annular broaching shoulders. Any suitable number of these grooves, such as from 2 to 8 or more may be milled in the tool to a depth such as from /2 to 1 inch, the bottom of the grooves being of any desired shape, such as arcuate, angular or flat, as shown in the drawing. The rims of the metal spirals 23 separate the grooves 21 from slicing edges 25 cooperating with the broaching edges 19 in cutting away the formation material of a keyslot wedging a drill string.

In operation, the present keyslot reamer is connected into a drill string at a desired distance above the drill collars and/or bit. The size of the reamer is chosen so that the diameter of the uppermost annular shoulder 19 is slightly greater than the diameter of the tool joints above it, while the diameter of the lowermost annular shoulder is slightly greater than that of the drill collars and bit therebelow. The drilling equipment is then operated in the normal manner with the present tool forming a part of the drill string.

If, during the drilling of a well, a keyslot is formed in a dog-leg portion of the borehole, and the drill string is wedged therein with the collars and drill bit below the obstruction, the drill string is pulled upwards to drag the present reamer through the keyslot. Since the reamer has no gradual taper, but a series of shoulders of stepwisely increasing diameter, it has no tendency to gradually wedge itself in the keyslot during the pulling operation, the series of cutting shoulders exercising a broaching action to which is added the slicing action of the spirally cut groove edges. If, on occasion, some difficulty is experienced in pulling the reamer through the keyslot, a rotary motion may be imparted to the drill string to unscrew the reamer from the keyslot by the reaction of the helical grooves with the formation. During this unscrewing action, the annular shoulders continue to exercise their broaching action. Due to the relatively sharp angle formed by the spiral grooves with the axis of the tool, this result is achieved much more rapidly and efliciently than in case of spirals formed nearly at right angles to the projected axis of the tool.

in the attached claims, that end of the reamer which is attachable to the upper portion of the drill string will be referred to as the upper end of the reamer, the other end being referred to as the lower end thereof.

I claim as my invention:

1. A keyslot reamer for use with a drill string above the drill bit and collars, said reamer comprising a tubular mandrel and provided with means at the upper and lower ends thereof for connecting said mandrel into a drill string, the outer face of said mandrel being formed as a plurality of adjoining cylindrical surfaces of progressively increasing diameters from the upper to the lower end of the mandrel and forming a plurality of annular shoulders perpendicular to the axis of the reamer, the peripheral edges of said shoulders constituting broaching cutters, and the outer face of said mandrel being provided with a spiral groove extending at an angle across and interrupting said cylindrical surfaces and shoulders, the edges of said groove constituting slicing cutters and cooperating with said broaching cutters to effect simultaneous slicing and broaching action when said reamer is moved upwardly through a well keyslot.

2. The device of claim 1, wherein the outside diameter of the smallest of said annular shoulders is slightly greater than the outside diameter of all tubular drill string elements connected above the keyslot reamer, and the outside diameter of the largest of said annular shoulders is slightly greater than the outside diameter of the drill collar elements connected below said keyslot reamer.

3. The device of claim 1, wherein the axial length of said adjoining cylindrical surfaces of stepwisely increasing diameters is substantially greater than the width of the annular shoulders between said adjoining cylinders.

4. The device of claim 1, wherein the width of said annular shoulder has a small value of the order of V of an inch.

References Cited in the file of this patent UNITED STATES PATENTS 

